Spinning of viscose



Dec. 26, R950 N. L. cox 2,535,044

SPINNING OF VISCOSE Filed April 26, 1947 INVENTOR. NORMAN LOUIS 00XATTORNEY Patented Dec. 26, 1950 UNITED STATES PATENT OFFICE SPINNING OFVISCOSE Norman Louis Cox, Claymont, Del., assignor to E. I. du Pont deNemours & Company, Wilmington, DeL, a corporation of DelawareApplication April 26, 1947, Serial No. 744,068

24 Claims. -(Cl. 18-54) This invention relates to the regeneration ofcellulose from viscose. More particularly it relates to a new processfor manufacturing regenerated cellulose articles such as filaments orfilms having improved properties. 1

Although the invention is generally applicable to the preparation offilaments, yarns, films, caps, bands, ribbons, and other structures ofregenerated cellulose, it will be discussed with particular reference tothe production of viscose rayon yarn.

It is known that the general strength and quality of viscose yarns areimproved through reduction of the primary swelling of the gel fibers.The great importance of the gel swelling factor in viscose spinningoperations has attained full recognition only in the last few years(see, for example U. S. 2,347,883 and 2,347,884). It is now recognizedthat, to constitute a commercially useful viscose rayon process, theviscose composition and the composition of the sulfuric acid coagulatingbath must be so balanced as to permit the production of regeneratedcellulose filaments having a gel swelling factor of not more than about6.5. It has been found that, for a given viscose, yarn properties suchas tenacity, elongation, softness, etc., are, as a rule, best whenspinning is done at or near the point of minimum gel swelling. It hasbeen found, moreover, that yarn properties are improved through methodsdesigned to reduce the gel swelling factor below the above-mentionedvalue of 6.5 and that, in general, the greater the reduction, the moremarked the improvements. Already proposed methods of reducing the gelswelling factor include the addition to the coagulating bath of zincsulfate or of ferrous, manganous, or chromic sulfates (U. S. Patents2,364,273; 2,347,883; and 2,347,884). While these methods representvaluable advances in the art, further improvements in yarn propertiesare needed.

It is well known that unripened viscoses, i. e., viscoses of salt indexof about 7 or higher, are not suitable for spinning by the methodscurrently used in the industry with normally ripened viscoses, i. e.,viscoses of salt index of about 5 to 6 or lower. This is attributed tothe high primary gel swelling of yarns from green viscoses, even thoughthe high degree of xanthation of green viscoses (which is reflected inproportionately high salt index values) has been thought desirable ontheoretical grounds for viscose spinning. A further problem, then, is tomake unripened viscose (the so-called green viscose) amenable tospinning. This is highly desirable since the use of unripened viscosewould result in decreasing or eliminating the ripening time nownecessary in manufacturing practice. Accordingly, methods for furtherreducing the gel swelling factor of unripened viscose, and inparticular, methods involving further improvements in yarn propertiesare particularly desirable.

An object of this invention is to provide a process of manufacturingregenerated cellulose filaments having gel swelling values lower thanheretofore attainable and exhibiting considerably improved yarnproperties. Another object is to provide a process whereby unripenedviscose can be spun in conventional spinning equipment to give yarn ofhigh quality. A further object is to provide a process of manufacturingregenerated cellulose yarn having entirely novel and desirableproperties. Yet a further object is the provision of a high tenacity,highly fatigue-resistant regenerated cellulose fiber having anon-crenulated surface and having improved soil and abrasion resistance.Other objects will appear hereinafter.

These objects are accomplished, in accordance with the invention, byextruding viscose into a sulfuric acid-sodium sulfate coagulating bathcontaining zinc sulfate and stretching the filaments, preferably in asecondary bath, said viscose containing dissolved therein at least 1millimole per grams of viscose of a monoamine soluble in 6% aqueoussodium hydroxide to the extent of at least 0.3%, the said monoaminehaving at least four carbon atoms but containing no radical of more thansix carbons.

Another object, which was unexpectedly found possible to accomplishthrough the invention described below was the production of very highstrength yarns having smooth (non-crenulated) surfaces with improvedsoil resistance and abrasion resistance. The combination of hightenacity and high fatigue resistance with smooth surface had notheretofore been achieved.

The use of certain secondary and tertiary amines in spinning baths or inviscose for preventing or reducing incrustation of spinnerets is known(Br. 533,309). However, the solubility in viscose of the agentsdisclosed is much too low (less than 0.1%) to cause a detectablereduction of the gel swelling. There was, therefore, no reason to expectthat the alkali-soluble amine modifiers of this invention would have anyeffect whatever on viscose spinning and/or yarn properties, and evenless reason to expect that their use would decrease gel swelling of theyarn below any previously known minimum and permit production, fromeither ripened or unripened viscose, of high tenacity filamentspossessing certain entirely new properties.

By the term alkali-soluble monoamine modifiers" is meant thosemonoamines having at least four carbon atoms but containing no radicalof more than six carbon atoms and being soluble in 6% aqueous sodiumhydroxide to an extent of at least 0.3%.

Referring to the drawings;

Figure 1 is a dyed cross section of a filament regenerated fromunripened, unmodified viscose, and

Figure 2 is a dyed cross section of a filament regenerated from viscoseunripened, modified with the agents of and by the processes of thisinvention.

The invention will be more clearly understood by referring to theexamples and discussion which follow. These examples are given forillustrative purposes and are not to be construed in any sense aslimitative. The numerical values of gel swelling given below for variousyarn samples were alldetermined according to the following procedure.The gel thread was collected in a mono-layer on a bobbin, by manuallyoperating a traverse mechanism with the thread being stretched 80% inthe hot dip bath. The sample was centrifuged (1400 R. P. M.) for aminute, cut off, and weighed in a closed bottle. The sample was washedfree of acid, dried in an oven at 105 C., and weighed. The ratio of thegel weight to cellulose weight (grams of gel per gram of cellulose) isreferred to as the gel swelling. Variations may be introduced in theprocedure, e. g., in the stretch, spinning speed, or length of bathtravel, but these introduce only minor changes in the numerical valuesof gel swelling.

Another important indication oi. yarn quality is the factor referred tobelow as D value. This factor relates to the rate of neutralization ofthe viscose filament in the coagulating and regenerating bath. It isdetermined by adding to the viscose a suitable indicator, in this casebromocresol purple (pH range 5.2 to 6.8), and observing the distance ininches from the spinneret at which the purple color completelydisappears in the traveling filament. This distance is the D value. Theselected amines suitable for use in this invention reduce the rate ofneutralization of the spinning filaments, hence increase the D valueover that of unmodified viscose. It has been found that, in general, thegreater the D value, the better the yarn properties. The increased D"value is believed to indicate that the modifying agents of thisinvention permit greater dehydration of the viscose before the gelstructure of the filament is permanently set.

Example I Viscose containing 1.8 millimoles of triethanolamine per 100grams of viscose is prepared in the following manner using 7% celluloseand 6% total sodium hydroxide (7-6 viscose). Alkali cellulose aged toget the desired viscose viscosity to poises) is xanthated for 2 hoursusing 35% CS: (based on the recoverable bone-dry cellulose). xanthatecrumbs are dissolved in a solution of caustic containing the modifier inamounts mentioned above. After mixing 1 hours at 0 C.. the freshlyprepared viscose is filtered while it is cold, deaerated, and kept at 0C. until spun, i. e., it is spun in the unripened state. as shown by thehigh salt index values, high xanthate sulfur content, and low sodiumtrithiocarbonate content. In all examples, the caustic content of 6%refers to the total alkalinity expressed as sodium hydroxide. Itincludes the amine modifier and the free sodium hydroxide, and thatcombined in the form of sodium carbonate, sodium trithiocarbonate, andsodium cellulose xanthate.

The viscose is spun into 275 denier-100 filament yarn by extrudingthrough a spinneret hav ing holes of 0.0025-inch diameter into a primarycoagulating and regenerating bath comprising 6.0% H2SO4, 14% Na2SO4, and15% ZnSO4. The yarn is given a bath travel of 28 inches by using aroller guide. The apparatus and general procedure used to lead viscoseinto the bath and to collect the formed thread are essentially the sameas those used commercially in the so-called bobbin or spool process. Thespecific conditions include a bath temperature of 50 C. and a first feedwheel speed of 485 inches per minute. The filaments are carried througha water bath at C. to C. and wound up at such a speed as to give 80%stretch beyond the feed wheel. The resulting regenerated gel yarn iswashed free of acid and salt and then processed. The yarns which aredried on the bobbin or, alternately, partially relaxed before drying byrewinding on another bobbin, are twisted 4 turns per inch and testedafter conditioning at 21 C. and 60% relative humidity for 48 hours.

The properties of the yarn prepared from the viscoses described hereinare listed in the accompanying table together, for comparison, withthose of unripened, unmodified viscose and. of ripened, unmodifiedviscose (the standard viscose of commercial operation), both controlsbeing spun under conditions identical to those for the modifiedviscoses. It will be seen that the gel swelling value is lowest and theD" value highest for the modified viscose. The physical properties,especially dry and wet tenacity, are higher than those for controlledviscoses.

The yarn produced by this and other examples has a number of propertieswhich distinguishes it sharply from other regenerated cellulose yarn.Its properties are similar to those produced through modification ofviscose with shortchain quaternary ammonium compounds which aredescribed and claimed in copending application Serial No. 716,415. Themost readily apparent modifications are the new cross-section andsurface features. For yarns prepared from unmodified viscose spun into azinc bath, a skin or outer shell which swells to a different extent inwater than that of the core is visible. These yarn cross-sections showboth deep and shallow crenulations around the contour of the filament.However, for yarns spun into zinc baths from viscose modified with theamine modifiers of this invention, the boundary between the skin andcore is very diffuse and crenulations are absent giving the yarn asmooth surface. The differences in cross-sections between modified Thefact that the filaments of the invention and improvement wet strengthare shown in the table below.

have smooth surface and considerably lower sec- Yarn Properties 3" gflmondary swelling (water take-up by dried yarns) results in moreresistance to iibrillating, launder- T ML, dry a 86 a 65 ing. fatiguingand sailing action than exhibited 1 fig. %.-.--.I.IIIIIIIZIIIIII ha 2113by normal crenulated viscose yarns. I E1on';., &een{dijj' 0.0 31:

, l Elong.,percent wet... 17.4 16.7 asses... i: Yarn Properties 3% g'gggg 233% "n" value,hi1:IIIIIIIII: 010 is .d., a. 3.55 3.45 i $3,513,2 5 1%3.3 a: 5 Example 7 f5 f fi5 3;? 1 3 An unripened '1-6 viscose containing2.5 mil- Eong percenhwet--- limoles of diethylaminoethanol is spun intoa fiflfig gff j'ffj 1 3 9-23-4 (HzSOk-NflsSOk-ZDSO) bath and the "D"v l.in---------- yarn is stretched and processed as in Example I. Thereduction in gel swelling and neutralization rates (increased D" value)and improved Example II yarn properties of the non-crenulated fibersthus A 7-6 viscose modified with 3.0 mlllimoles of tamed are the tablebelowtriethylamine per 100 grams oi viscose is prepared and spun in themanner described in Ex- U I d UM ad I ample I. In this case. however,the coagulating Yam Pmpem 1: 111 331 lllll l lggl flfld bath is 9-23-4(HzSO4Na2SO4ZnSO4). The yarn properties are tabulated below along with Tms-Id, dry 3.92 3.85 those oi green, unmodified and ripened, control $33513;; m3; ggg 5 53 viscose. Itwill be noted that the use of un-Eiong.,peroent ry 6.5 1.1 ripened, modified viscose gives lower gelswell- E2351; :23: {53a ;;2 2;; ing, lower rate of neutralization(higher "D" g lswe s 2- 3.2 value) and improved yarn properties. D valueM u Unri ned Unripened Ripened as Example VI Yam Properties m med mmdmemmwmed A cotton llnters viscose containing 7% cellu- T m dry 3 74 3 3 wlose, 6% total caustic, and 1.8 millimoles o! triethanolamine per 100grams of viscose is pre- 'r .d., z 2.53 2.13 2.20 i gi, 55s., 123

1 s o pared and ripened to a salt index of 5.0 as is normally done incommercial production and then l i t 3.3 Q6 3.0 spun into filamentsusing all conditions of Ex- 9gn g if, 3;: ample I for collection andprocessing with the exception that an 8-23-4 4 5 (H2SO4Naa$O4-ZnSO4)Example III A cotton llnters viscose containing 7% cellulose, 6% sodiumhydroxide, and 2.9 milllmoles oi diethanolamine per 100 grams of viscoseis prepared and spun as described in Example I. Yarns with smoothsurface and improved physical properties (see table below) wereobtained.

Yarn Properties m 21 gi gfi gi Ten., g./d., Ten., g.ld., wet 'len.,g./d., loop Elong., per cent dry Elong., per cent wet r cent loop Gelswe Elong.,

D" value, in l- Example IV bath instead of an 8-44-15 was used. Aconsiderable decrease in gel swelling and increase in "D" value areobtained which are reflected in a n measurable increase in physicalproperties of the yarn (table below). The character of the filament ischanged in the same manner as noted with unripened viscoses.

.u-c viscose modified with 3.5 millimoles of cyclohexylamine per 100grams of viscose is prepared and spun and the yarns are processed in themanner described in Example I. In'this case,

however, the coagulating bath is 8-23-4 (Hesoe-Naesoi-znsoi) As may beseen in the table below the wet strength is better than for theaccompanying control and the rate of neutralization and gel swelling aremuch lower.

ned Unri ned Yarn Properties 3 ed gg d 3.83 3-8] 2. 74 2. 11 2-8) 2.966.2 7. l 20. l 17. l 3.0 4. 7 2.49 3.23 "D" value, in 7.0 3.

Example VIII A cotton linters viscose containing 7% cellulose and 6%sodium hydroxide and 4.5 millimoles of n-amylamine per 100 grams ofviscose is prepared as described in Example I. The viscose is spun in anunripened state in 8-23-4 bath and all conditions of Example I forspinning and processing are used. The table below shows the improvementin loop and wet tenacities and gel swelling obtained from this modifier.

Unrl ned, modfled Yarn Prop unmodified Ten., g.ld., wet. Ten., g.ld.,loop... Elong., per cent dry. Elong., per cent wet... Elong., r centloop. Gel swe ling "D" value, in

. -sef swws M s- 9mm ea asa of at least 0.3% is suitable, provided italso fulfills the other conditions previously stated, namely (a) It mustbe a monoamine. It has been found that certain diamines, e. g. ethylenediamine have practically no effect as regards decrease in gel swellingand increase in D" value.

(b) It must have at least four carbon atoms. Lower amines such asmethylamlne or ethylamine are substantially ineffective.

(c) It must have no radical of more than six carbon atoms. Largerradicals, in addition to decreasing the solubility of the amine, tend toproduce surface-activity which is not desirable in the process of thisinvention.

The preferred modifiers are those in which the amino nitrogen isattached to hydrocarbon groups, preferably alkyl groups, and/or tohydroxyalkyl groups.

An obvious requirement besides solubility is that modifiers must besubstantially chemically inert and unaffected by components of theviscose before coagulation. Suitable agents which may be mentioned inaddition to those used in the examples are diethylamine, dipropylamine,butyl- Unripeued. f

' 8 amine, ethyldiethanolamine, dipropanolamine, propylpropanolamine,hexanolamine, amyldiethanolamine, butylmethylethanolamine.propylethanolamine, cyclohexylethanolamine, hexamethyleneimine,piperidine, pyridine, and hexyldiethanolamine.

The amine modifiers for effective results should be used in the viscosein concentrations of at least 1.0 milllmole of agent per 100 grams ofviscose, and, in general, it is unnecessary to use more than 10millimoles of agent per 100 grams of viscose, a generally useful rangebeing 1.0 to 4.0 millimoles per 100 grams of viscose. In terms of theless informative weight percent basis there should be used between 0.1and 1.0% of the modifying agent. The optimum concentration of any givenagent depends on its eflectiveness and on its molecular weight. Forexample, larger concentrations of diethylamine are needed than fortriethylamine. It also depends to'some extent on process variables suchas the spinning speed, since at high spinning speeds used in industrialpractice less agent is desired than at lower speeds. for the reasonthatthe rate of neutralization of the filament should be retarded onlyto the extent compatible with complete coagulation during the short timethe filament is in contact with the coagulating bath. Determination ofthe optimum concentration of the amine compound is a matter of simpleexperimentation for those skilled in the art.

The viscose used in the process of the invention may be of a variety oftypes: for example, it may be from wood pulp, cotton linters, mixturesof the two, or even other types of cellulose. The composition of theviscose may also be varied widely. For example, it may have a cellulose.content of from 4% to 10% or even more and an alkali content of from 4%to 8% or more. The standard viscoses of the industry, 1. e., thosehaving between 5% and 7% cellulose and between 4% and 6% alkali, arepreferably used. The amount of carbon disulfide used in xanthation canbe from 25% to 50% (based on the recoverable bone-dry cellulose). It hasbeen found that higher than normal xanthate sulfur contents (higher saltindices) can be used in the viscose when the amines described herein areadded and there appears to be an advantage in stretchability and levelof yarn properties if salt indices higher than 5 are used. It isnecessary to use 30% or greater amounts of carbon disulfide to obtainsalt indices of 5 or over in unripened viscoses. Thus, one of the chiefadvantages of the invention is that unripened or partially ripenedviscoses may be used, with the result that the ripening time and spacenow required in viscose plants may be eliminated or substantiallyreduced.

While the use of unripened viscose is of special interest in the processof this invention, it has been shown (Example VI) that notableimprovements in yarn quality are also obtained with normally ripenedviscose, thus making the process directly applicable to existing plantpractice.

The spinning baths suitable for use in the invention contain sulfuricacid, sodium sulfate, and zinc sulfate. Zinc sulfate is an essentialcomponent of the spinning bath since, in its absence, the aminecompounds have no effect on spinning and yarn properties. If desired,additional salts of divalent metals known to reinforce or supplement theaction of zinc sulfate may be used, such as ferrous sulfate, manganesesulfate, nickel sulfate, or chromic sulfate. particularly thefirst-named salt. The use of these divalent metal salts makes itpossible to use smaller amounts of zinc sulfate than are necessary intheir absence. Preferably, the spinning bath contains from 4% to 12% ofsulfuric acid, from 13% to 25% of sodium sulfate, and from 2% to 15% ofzinc sulfate, optionally with 1% to about of ferroussulfate. The optimumquantity of zinc sulfate from the standpoint of practical spinningspeeds, reduction in gel swelling, and extent of modification ofphysical properties of yarn appears to be 3% to 5%. with the addition ofamines toviscose, it is possible to The novel and improved yarnsobtainable through the process of this invention can, in general, beused instead of regular regenerated cellulose fibers for any purposewhere the latter are finding applications, more particularly in thetextile and tire cord industries.

\Any departure from the above description which conforms to the presentinvention is intended to be included within'the scope of the bathacidity under which conditions normal, un-

modified viscoses give yarns of decreased quality.

The temperature range of best spinnability is from 40 C. to 65 C. On thebasis of available data, it is desirable to have the bath acidity andtemperature as low as is practical for a given spinning speed in orderto get optimum filament structure and yarn properties. Each of the aboveconcentrations should be adjusted to each other and to the compositionof the viscose. It is desirable to use as hi h a total solids content aspossible in the coagulating bath to give the highest degree of gelshrinkage and improved stretchability.

The fila ents mav be given a long travel of 130 to 250 inches in theprimary bath by means of a multiple roller setup which gradually appliestension to the traveling filaments and thereby orients them while theyare still plastic. The preferred method, however, is to apply a part orall of the stretch beyond the primary bath in a secondary bath or to u ea combination of air and hot bath stretch. The secondary bath mayconsist simply of water or of dilute (1% to 3%) sulfuric acid, or it mayhave the same composition as the coagulating bath but at a greaterdilution, e. g., one-fourth of the concentration of the coa ulatingbath. The temperature of the secondary bath is preferably between 50 C.and 100 C. Stretches of 80% to 100% are preferred for producing hightenacity yarn and to for textile type yarns. The bobbin process has beenused in the example. but it is immaterial whether spinning is by bobbin,bucket, or continuous processes. The yarn cake is washed free of acidand salt and then dried under tension. If preferred, it may be twisterorsla her-dried to enable the dry elongation of the fini hed product to becontrolled. When using the two-bath s inning system, the preferredprocedure is to draw off the freshly coagulated gel yarn with a feedwheel speed equal to or less than the jet velocity and to ap ly all ofthe stretch between positively driven rollers traveling at differentspeeds. The thread can be given a travel of 10 to inches in thesecondary bath of hot water or dilute bath. As mentioned above, theamount of stretch applied depends on the properties desired for theyarn.

0n the basis of available data, it is thought probable that themechanism by which amine compounds influence the spinning process isthrough interaction with zinc sulfate on the one hand and with thesodium trithiocarbonate of the viscose on the other hand. It has not yetbeen possible to determine whether this effect on filament formation isaccomplished through (1) bufier action, (2) transient formation of insoluble complexes, which might exercise some control on the porosity ofthe initial skin which is set up, or (3) other colloidal eflects.

claims.

I claim: 1. A method of producing regenerated cellulosic structureswhich comprises spinning viscose per grams of viscose of an aliphaticmonoamine having at least four carbon atoms but containing no radical ofmore than six carbon atoms and being soluble in 6% aqueous sodiumhydroxide to theextent of at least 0.3% in an aqueous sulfuric acidspinning bath containing from 1% to 15% zinc sulfate.

3. In a method of producing regenerated cellulosic structures byextruding viscose in an aque" ous sulfuric acid bath containing from 1%to 15% zinc sulfate, the step which comprises inbut containing noradical of more than six carbon atoms and being soluble in 6% aqueoussodium hydroxide to the extent of at least 0.3%.

4. A method of producing regenerated cellu-i losic structures whichcomprises incorporating .in

viscose at least 1 millimole per 100 grams of viscose of an aliphaticmonoamine having at least four carbon atoms but containing no radical ofmore than six carbon atoms and being soluble in 6% aqueous sodiumhydroxide to the extent of at least 0.3%, extruding the resultantviscose into a coagulating bath comprising an aqueous solution of 4% to12% sulfuric acid, 13% to 25% sodium sulfate, and 1% to 15% zincsulfate;

6. A process as defined in claim 5 in which the said structures arepassed into a second bath and stretched to an extent of at least 20%.

7. Viscose containing at least 1 millimole per 100 grams of viscose ofan aliphatic monoamine having at least four carbon atoms but containingno radical of more than six carbon atoms and being soluble in 6% aqueoussodium hy-- droxide to the extent of at least 0.3%.

8. Viscose having a salt index of at least 5 and conta ning at least onemillimole per 100 grams assume 11 i of viscose of an aliphatic monoaminehaving at least four carbon atoms but containing no radical of more thansix carbon atoms and being soluble in 6% aqueous sodium hydroxide to theextent of at least 0.3%. V

9. Viscose containing 4% to cellulose combined as sodium cellulosexanthate with from 25% to 50% carbon disulflde, 4% to 8% of sodiumhydroxide and at least one millimole per 100 grams of viscose of analiphatic monoamine having at least four carbon atoms but containing noradical of more than six carbon atoms and bein soluble in 6% aqueoussodium hydroxide to the extent of at least 0.3%.

10. A method of producing regenerated cellulosic structures whichcomprises spinning unripened viscose containing at least one millimoleper 100 grams of unripened viscose of an aliphatic monoamine having atleast four carbon atoms but containing no radical of more than 'sixcarbon atoms and being soluble in 6% aqueous sodium hydroxide to theextent of at least 0.3% in an aqueous sulfuric acid spinning bathcontaining from 1% to zinc sulfate.

11. A method of producing regenerated cellulosic structures whichcomprises spinning unripened viscose containing from about 1 to about 4millimoles per 100 grams of unripened viscose of an aliphatic monoaminehaving at least four carbon atoms but containing no radical of more thansix carbon atoms and being soluble in 6% aqueous sodium hydroxide to theextent of at least 0.3% in an aqueous sulfuric acid spinning bathcontaining from 1% to 15% zinc sulfate.

12. In a method of producing regenerated cellulosic structures byextruding unripened viscose in an aqueous sulfuric acid bath containingfrom 1% to 15% zinc sulfate, the step which comprises incorporating inthe said unripened viscose at least 1 millimole per 100 grams ofunripened viscose of an aliphatic monoamine having at least four carbonatoms but containing no radical of more than six carbon atoms and beingsoluble in 6% aqueous sodium hydroxide to the extent of at least 0.3%.

13. A method of producing regenerated cellulosic structures whichcomprises the steps of spinning unripened viscose containing at leastone millimole per 100 grams of unripened viscose of an aliphaticmonoamine having at least four carbon atoms but containing no radical ofmore than six carbon atoms and being soluble in 6% aqueous sodiumhydroxide to the extent of at least 0.3% in an aqueous sulfuric acidspinning bath containing from 1% to 15% zinc sulfate; passing saidstructures into a second bath and stretching said structures to anextent of at least 14. A process of producing regenerated cellulosicstructures which comprises incorporating in unripened viscose at least 1millimole per 100 grams of unripened viscose of an aliphatic monoaminehaving at least fo r carbon atoms but containing no radical of more thansix carbon atoms and being soluble in 6% aqueous sodium hy-r droxide tothe extent of at least 0.3%. extrudins the resultant unripened viscoseinto a coagulating bath comprising an aqueous solution of 4% to 12%sulfuric acid, 13% to 25% sodium sulfate, and 1% to 15% zinc sulfate.

15. A process as defined in claim 14 in which the said structures arepassed into a second bath and stretched to an extent of at least 20%.

16. Unripened viscose containing at least 1 millimole per grams ofunripened viscose of an aliphatic monoamine having at least four carbonatoms but containing no radical of more than six carbon atoms and beingsoluble in 6% aqueous sodium hydroxide to the extent of at least 0.3%.

17. Unripened viscose having a salt index of at least 5 and containingat least one millimole per 100 grams of unripened viscose of analiphatic monoamine having at least four carbon atoms but containing noradical of more than six carbon atoms and being soluble in 6% aqueoussodium hydroxide to the extent of at least 0.3%.

18. Unripened viscose containing 4% to 10% cellulose combined as sodiumcellulose xanthate with from 25% to 50% carbon disulflde, 4% to 8% ofsodium hydroxide and at least one millimole per 100 grams of unripenedviscose of an aliphatic monoamine having at least four carbon atoms butcontaining no radical of more than six carbon atoms and being soluble in6% aqueous sodium hydroxide to the extent of at least 0.3%.

19. A method in accordance with claim 1 in which the said monoamine isn-amylamine.

20. A method in accordance with claim 1 in which the said monoamine iscyclohexylamine.

21. A method in accordance with claim 1 in which the said monoamine isbutylmonoethanolamine.

22. Viscose in accordance with claim 7 in which the said monoamine isn-amylamine.

23. Viscose in accordance with claim 7 in which the said monoamine iscyciohexylamine.

24. Viscose in accordance with claim 7 in which the said monoamine isbutylmonoethanolamine.

NORMAN IDUIS COX.

nsmaancss crrsn The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,877,933 Meyer Sept. 20, 19321,880,514 Staud et a1. Oct. 4, 1932 1,984,303 Hardt Dec. 11, 19342,069,805 Heckert Feb. 9, 1937 2,125,031 Polak July 26, 1938 2,310,207Bley Feb. 9, 1943 2,340,377 Graumann et a1. Feb. 1, 1944 2,364,273 CoxDec. 5, 1944 Certificate of Correction Patent N 0. 2,535,044 December26, 1950 NORMAN LOUIS COX It is hereby certified that error appears inthe printed specification of the above numbered patent requiringcorrection as follows:

Column 5, lines 68 and 69, for the Word butylmonolamjne readbutylmonoetlmnolamz'ne; column 6, line 67, for A7-6 read A 76; column 7,line 15, for collulose read cellulose; and that the said Letters Patentshould be read as corrected above, so that the same may conform to therecord of the case in the Patent Ofiice.

Signed and sealed this 22nd day of May, A. D. 1951.

THOMAS F. MURPHY,

Assistant Commissioner of Patents

1. A METHOD OF PRODUCING REGENERATED CELLULOSIC STRUCTURES WHICHCOMPRISES SPINNING VISCOSE CONTAINING AT LEAST ONE MILLIMOLE PER 100GRAMS OF VISCOSE OF AN ALIPHATIC MONOAMINE HAVING AT LEAST FOUR CARBONATOMS BUT CONTAINING NO RADICAL OF MORE THAN SIX CARBON ATOMS AND BEINGSOLUBLE IN 6% AQUEOUS SODIUM HYDROXIDE TO THE EXTENT OF AT LEAST 0.3% INAN AQUEOUS SULFURIC ACID SPINNING BATH CONTAINING FROM 1% TO 15% ZINCSULFATE.